| CPC H10N 70/011 (2023.02) [H10B 63/24 (2023.02); H10N 70/24 (2023.02); H10N 70/826 (2023.02)] | 8 Claims |

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1. A method comprising:
forming a bottom electrode layer over a substrate;
forming a mixed ionic-electronic conductor (MIEC) layer including copper, germanium, and sulfur in direct contact with the bottom electrode layer
forming a middle electrode layer over the MIEC layer;
forming a metal oxide layer over the middle electrode layer;
forming a first top electrode layer and a second top electrode layer over the metal oxide layer, the first top electrode layer, the second top electrode layer, and the metal oxide layer forming a stack; and forming sidewall spacers on sidewalls of the stack such that the sidewall spacers are positioned directly in contact with a surface of the middle electrode layer, and, in their entirety, over the surface of the middle electrode layer.
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